text: The reduction of tropinone is mediated by NADPH-dependent reductase enzymes, which have been characterized in multiple plant species.  These plant species all contain two types of the reductase enzymes, tropinone reductase I and tropinone reductase II.  TRI produces tropine and TRII produces pseudotropine.  Due to differing kinetic and pH/activity characteristics of the enzymes and by the 25-fold higher activity of TRI over TRII, the majority of the tropinone reduction is from TRI to form tropine.